Which parameter is most directly used to estimate range per unit of fuel?

• A. Density altitude.
• B. Specific range.
• C. Vne.
• D. Vref.

Answer: (B)

Specific range directly expresses how far an aircraft can travel for each unit of fuel burned. It’s defined as the distance divided by the amount of fuel (for example, NM per pound or NM per kilogram), so it links fuel load to potential travel in a single, actionable value. When you plan a flight, you use the specific range under the expected cruise conditions, then multiply it by the available fuel to estimate the achievable range. Density altitude influences performance and thus can affect the SR, but it isn’t the ratio itself. The other options are speeds used for other purposes and don’t quantify distance per fuel.